In general terms, geothermal energy is thermal energy (the energy that determines the temperature of matter) generated and stored in the Earth. The geothermal energy of the Earth's crust originates from the original formation of the planet and from radioactive decay of minerals, resulting in continual production of geothermal energy below the earth's surface.

In terms of alternative energy, geothermal energy is the energy that is harnessed from the Earth's internal heat and used for practical purposes, such as heating buildings or generating electricity. It also refers to the technology for converting geothermal energy into useable energy. The term geothermal power is used synonymously as the conversion of the Earth's internal heat into a useful form of energy, or more specifically as the generation of electricity from this thermal energy (geothermal electricity).

Geothermal provides a huge, reliable, renewable resource, unaffected by changing weather conditions. However, geothermal also faces a number of challenges, including the need for significant capital investment, and a significant amount of time in terms of building geothermal plants.

Deontological ethics recognizes a number of distinct duties, such as those proscribing the killing of innocent people (murder) and prohibitions on lying and promise breaking. Deontology maintains that the wrongness of (some) actions is intrinsic, or resides in the kind of action that it is, rather than the consequences it brings about. So, for example, an act of killing an innocent man is wrong because it is the killing of an innocent man, rather than because it deprives someone of future happiness and causes grief to a family. In this, deontological ethics is opposed to consequentialism, which defines the moral rightness of an action in terms of the consequences it brings about.